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Bretisilocin

Bretisilocin (GM-2505), a serotonergic psychedelic tryptamine analogue of DMT, is under development for major depressive disorder. The drug acts as a potent 5-HT2A/2C receptor agonist and serotonin releasing agent, producing hallucinogenic effects in humans via intravenous infusion.

read10 min publishedJun 15, 2026

| Clinical data | |

|---|---|
| Other names | GM-2505; GM2505; 5-Fluoro-N-methyl-N-ethyltryptamine; 5F-MET; 5-F-MET; 5-Fluoro-MET |

administration |

Intravenous,[1][2][3][4]intranasal[5]Drug class

Serotonergic psychedelic;Hallucinogen;Serotonin5-HTand2A5-HT2Creceptoragonist;Serotonin5-HT2Breceptorpartial agonistorantagonist;Serotonin releasing agentLegal status

  • Investigational
[Pharmacokinetic](/wiki/Pharmacokinetics)data

[Onset of action](/wiki/Onset_of_action)

[IV](/wiki/Intravenous_injection): 10–20 minutes ([peak](/wiki/Tmax_(pharmacology)))[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)[Elimination half-life](/wiki/Biological_half-life)

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)[[3]](#cite_note-HughesChristianDvorak2023-3)[Duration of action](/wiki/Pharmacodynamics#Duration_of_action)

[IV](/wiki/Intravenous_injection): 60–90 minutes[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)[[6]](#cite_note-Peplow2024-6)*N*-ethyl-2-(5-fluoro-1*H*-indol-3-yl)-*N*-methylethanamine

[CAS Number](/wiki/CAS_Registry_Number)

[PubChem](/wiki/PubChem#CID)CID

[ChemSpider](/wiki/ChemSpider)

[ChEMBL](/wiki/ChEMBL)

[Formula](/wiki/Chemical_formula)

13H17FN2[Molar mass](/wiki/Molar_mass)

−1[JSmol](/wiki/JSmol))

- CCN(C)CCC1=CNC2=C1C=C(C=C2)F

- InChI=1S/C13H17FN2/c1-3-16(2)7-6-10-9-15-13-5-4-11(14)8-12(10)13/h4-5,8-9,15H,3,6-7H2,1-2H3
- Key:XRWQULAXCLVBPP-UHFFFAOYSA-N

**Bretisilocin**, also known by its developmental code name **GM-2505** and as **5-fluoro- N-methyl-N-ethyltryptamine** (

5F-MET or

**5-fluoro-MET**), is a

[serotonergic psychedelic](/wiki/Serotonergic_psychedelic)of the

tryptaminefamily which is under development for the treatment of

[major depressive disorder](/wiki/Major_depressive_disorder).

[[1]](#cite_note-AdisInsight-1)

[[7]](#cite_note-WitkinGolaniSmith2023-7)

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)It is an

[[3]](#cite_note-HughesChristianDvorak2023-3)[analogue](/wiki/Structural_analog)of

[dimethyltryptamine](/wiki/Dimethyltryptamine)(DMT) and is the 5-

[fluorinated](/wiki/Fluorine)

[derivative](/wiki/Chemical_derivative)of

[methylethyltryptamine](/wiki/Methylethyltryptamine)(MET).

Bretisilocin's

[[8]](#cite_note-US11440879B2-8)[route of administration](/wiki/Route_of_administration)is

[intravenous infusion](/wiki/Intravenous_infusion).

[[1]](#cite_note-AdisInsight-1)

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)

[[3]](#cite_note-HughesChristianDvorak2023-3)

[[4]](#cite_note-UmbrichtChristianWinters2024-4)The drug acts as a [potent](/wiki/Potency_(pharmacology)) and well-balanced [serotonin](/wiki/Serotonin) [5-HT 2A](/wiki/5-HT2A_receptor) and

[5-HT](/wiki/5-HT2C_receptor)

2Creceptor[agonist](/wiki/Agonist), serotonin

[5-HT](/wiki/5-HT2B_receptor)

2Breceptor[partial agonist](/wiki/Partial_agonist)or

[antagonist](/wiki/Receptor_antagonist), and

[serotonin releasing agent](/wiki/Serotonin_releasing_agent).

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)

[[9]](#cite_note-HughesKleinAustin2022-9)

[[8]](#cite_note-US11440879B2-8)It produces psychedelic-like effects in animals and similarly produces robust

[[10]](#cite_note-WO2022256554-10)[hallucinogenic](/wiki/Hallucinogen)effects in humans.

[[9]](#cite_note-HughesKleinAustin2022-9)The

[[3]](#cite_note-HughesChristianDvorak2023-3)[duration](/wiki/Duration_of_action)of bretisilocin is 60 to 90 minutes and is intermediate between the durations of DMT and

[psilocybin](/wiki/Psilocybin).

[[6]](#cite_note-Peplow2024-6)

[[11]](#cite_note-HughesKleinDvorak2023-11)

[[4]](#cite_note-UmbrichtChristianWinters2024-4)

[[12]](#cite_note-Gunther2023-12)

[[8]](#cite_note-US11440879B2-8)It has been regarded by its developer as an "improved version of DMT".

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)

[12]Bretisilocin was invented by Andrew Kruegel at Gilgamesh Pharmaceuticals and was patented in 2021.[9] [10] It is under development by Gilgamesh Pharmaceuticals.

As of June 2025, the drug is in

[[1]](#cite_note-AdisInsight-1)[phase 2](/wiki/Phases_of_clinical_research#Phase_II)

[clinical trials](/wiki/Clinical_trial)for the treatment of

[major depressive disorder](/wiki/Major_depressive_disorder).

Bretisilocin was acquired from Gilgamesh Pharmaceuticals by

[[1]](#cite_note-AdisInsight-1)[AbbVie](/wiki/AbbVie)in a deal worth up to $1.2 billion in August 2025.

[[13]](#cite_note-Taylor2025b-13)It was encountered as a novel

[[14]](#cite_note-PsychedelicAlpha2025b-14)[recreational](/wiki/Recreational_drug)

[designer drug](/wiki/Designer_drug)in 2026.

[[5]](#cite_note-Aipsin-5)## Use and effects

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=1)]

Bretisilocin, given by intravenous injection, produces threshold psychedelic effects at doses of 1 mg and 3.3 mg, has an optimal dose range of 10 to 15 mg, and produces particularly intense effects at a dose of 20 mg. [2] The drug's effects at doses of 15 to 20 mg intravenously were described as equivalent to or greater than those of 30 mg

[psilocybin](/wiki/Psilocybin)

[orally](/wiki/Oral_administration)or 100 to 200 μg

[LSD](/wiki/LSD)orally based on

[hallucinogen rating scales](/wiki/Hallucinogen_rating_scale).

The 20 mg dose of bretisilocin was associated with more

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)[challenging experiences](/wiki/Challenging_experience)including

[anxiety](/wiki/Anxiety),

[cognitive impairment](/wiki/Cognitive_impairment), and dread of

ego dissolution, which led to selection of a lower optimal dose range of 10 to 15 mg intravenously.

Compared to other psychedelics like psilocybin and LSD, bretisilocin has a much shorter

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)[duration](/wiki/Duration_of_action), but is longer-lasting than

[dimethyltryptamine](/wiki/Dimethyltryptamine)(DMT).

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)

[[11]](#cite_note-HughesKleinDvorak2023-11)

[4]Its duration is about 60 to 90 minutes, whereas psilocybin has a duration of multiple hours and DMT has a duration of as short as 10 minutes.

[[8]](#cite_note-US11440879B2-8)

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)

[6]The psychedelic effects of bretisilocin are generally resolved by approximately 2 hours after administration, but have been found to last up to 4 to 6 hours in some individuals.

[[12]](#cite_note-Gunther2023-12)Peak effects occur about 10 to 20 minutes following injection.

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)

[2]The drug, administered intravenously in clinical studies, produces effects in humans including "altered states of consciousness, altered visual depth perception, abnormal thinking, euphoric mood, feeling drunk, feeling of body temperature changes, relaxation, sensory processing disorder (including intense visual effects with color changes), sensory overload, and time perception altered".[2][3] [4] The subjective effects of bretisilocin were described as very robust and consistent in strength with the effects of other psychedelics including LSD, DMT, and psilocybin as have been reported in clinical studies.

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)

[[3]](#cite_note-HughesChristianDvorak2023-3)In addition to intravenous administration, bretisilocin has been

[[4]](#cite_note-UmbrichtChristianWinters2024-4)[anecdotally reported](/wiki/Anecdotal_report)by recreational users to be active

[intranasally](/wiki/Intranasal_administration).

[[5]](#cite_note-Aipsin-5)## Side effects

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=2)]

Side effects of bretisilocin include acute sensory processing disorder, altered state of consciousness, abnormal thinking, euphoric mood, fatigue, and small increases in heart rate and blood pressure, among others.[2][3] [4] Adverse effects like fatigue and

headacheoccur after the psychedelic experienceand can persist for up to 24 hours after administration.

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)## Interactions

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=3)]

Pharmacology #

[edit]

Pharmacodynamics

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=5)]

Bretisilocin acts as a [potent](/wiki/Potency_(pharmacology)) and well-balanced [serotonin](/wiki/Serotonin) [5-HT 2A](/wiki/5-HT2A_receptor) and

[5-HT](/wiki/5-HT2C_receptor)

2Creceptor[agonist](/wiki/Agonist), serotonin

[5-HT](/wiki/5-HT2B_receptor)

2Breceptor[antagonist](/wiki/Receptor_antagonist), and

[serotonin releasing agent](/wiki/Serotonin_releasing_agent).

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)

[[9]](#cite_note-HughesKleinAustin2022-9)In another study however, it was a moderate-

[[10]](#cite_note-WO2022256554-10)[efficacy](/wiki/Maximal_efficacy)

[partial agonist](/wiki/Partial_agonist)of the serotonin 5-HT

2Breceptor.

The drug appears to have negligible activity as a serotonin

[10]5-HTagonist. 1AreceptorHowever, another study found that it was a serotonin 5-HT

[[9]](#cite_note-HughesKleinAustin2022-9)1Areceptor

[full agonist](/wiki/Full_agonist), with an

[EC](/wiki/Half-maximal_effective_concentration)at this receptor that was about 44-fold less

50[potent](/wiki/Potency_(pharmacology))than at the serotonin 5-HT

2Areceptor.

[10]The affinity (Ki) of bretisilocin for the serotonin 5-HT2A receptor was 4.9 nM with DOI as the radioligand and 140–191 nM with ketanserin as the radioligand.[2] [9] Its

[EC](/wiki/Half-maximal_effective_concentration)(

50[E](/wiki/Maximal_efficacy)) values were 15.0–20.6 nM (80.6–87.6%) at the serotonin 5-HT

max2Areceptor and 9.5 nM (85.1%) at the serotonin 5-HT

2Creceptor, whereas its

ICat the serotonin 5-HT 502Breceptor was 5.8 nM.

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)It showed much higher

[[9]](#cite_note-HughesKleinAustin2022-9)[efficacy](/wiki/Maximal_efficacy)at the serotonin 5-HT

2Areceptor than its

[parent compound](/wiki/Parent_compound)

[MET](/wiki/Methylethyltryptamine)(E

max= 87.6% vs. 36.2%, respectively).

Bretisilocin showed very weak activity at the serotonin 5-HT

[8]1Areceptor (EC 50= 16,918 nM, E

max= 83.0%).

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)

[[9]](#cite_note-HughesKleinAustin2022-9)In addition to its actions at the serotonin

[[8]](#cite_note-US11440879B2-8)[5-HT](/wiki/5-HT2_receptor), it is a

2receptorspartialserotonin releasing agent in rat brain

synaptosomes, with an EC 50of 8.4–15.7 nM and an E

maxof 66.8–71.4%.

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)

[[9]](#cite_note-HughesKleinAustin2022-9)Bretisilocin is also a

[[8]](#cite_note-US11440879B2-8)[serotonin reuptake inhibitor](/wiki/Serotonin_reuptake_inhibitor)to a much weaker extent (IC

50= 418.9 nM).

Additional values have also been published.

[[8]](#cite_note-US11440879B2-8)

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)

[10]Bretisilocin is related to DMT and is considered by its developer to be an "improved version of DMT".[2] [12] It also induces more serotonin release than DMT, which may provide it with more

[entactogen](/wiki/Entactogen)-like qualities compared to DMT.

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)Bretisilocin produces the

[[12]](#cite_note-Gunther2023-12)[head-twitch response](/wiki/Head-twitch_response), a behavioral proxy of psychedelic effects, in rodents.

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)

[[9]](#cite_note-HughesKleinAustin2022-9)

[[3]](#cite_note-HughesChristianDvorak2023-3)It shows

[[8]](#cite_note-US11440879B2-8)[antidepressant](/wiki/Antidepressant)-like effects in rodents.

[[9]](#cite_note-HughesKleinAustin2022-9)The drug

[[11]](#cite_note-HughesKleinDvorak2023-11)[dose-dependently](/wiki/Dose_dependence)produces

hypolocomotionin rodents similarly to many other serotonergic psychedelics.

[[8]](#cite_note-US11440879B2-8)Likewise, it produces

[[15]](#cite_note-HalberstadtGeyer2018-15)[anti-obsessional](/wiki/Anti-obsessional)effects in the form of reduced

[marble burying](/wiki/Marble_burying)in rodents.

Bretisilocin does not produce

[[8]](#cite_note-US11440879B2-8)[conditioned place preference](/wiki/Conditioned_place_preference)(CPP) in rodents, suggesting lack of

[reinforcing](/wiki/Positive_reinforcement)properties.

[[8]](#cite_note-US11440879B2-8)### Pharmacokinetics

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=6)]

The [pharmacokinetics](/wiki/Pharmacokinetics) of bretisilocin have been studied.[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2) [3] The

[time to peak](/wiki/Tmax_(pharmacology))concentrations with

[intravenous injection](/wiki/Intravenous_injection)is 10 to 20 minutes.

Its

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)[elimination half-life](/wiki/Elimination_half-life)is approximately 45 minutes (range 40 to 50 minutes).

[[2]](#cite_note-MarekMakai-BölöniUmbricht2025-2)

[[3]](#cite_note-HughesChristianDvorak2023-3)## Chemistry

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=7)]

Bretisilocin, also known as 5-fluoro-*N*-methyl*-N*-ethyltryptamine, is a [substituted tryptamine](/wiki/Substituted_tryptamine) [derivative](/wiki/Chemical_derivative). [8] It is a derivative of

[dimethyltryptamine](/wiki/Dimethyltryptamine)(DMT) and

[methylethyltryptamine](/wiki/Methylethyltryptamine)(MET) as well as of

[5-fluorotryptamine](/wiki/5-fluorotryptamine)(5-FT).

[[6]](#cite_note-Peplow2024-6)

[[8]](#cite_note-US11440879B2-8)### Synthesis

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=8)]

The [chemical synthesis](/wiki/Chemical_synthesis) of bretisilocin has been described.[[10]](#cite_note-WO2022256554-10)

Analogues

[edit] Some analogues of bretisilocin include 5-fluoro-DMT, 5-fluoro-DET, 5-fluoro-EPT, 5-chloro-DMT, 5-bromo-DMT, 5-fluoro-AMT, 5-fluoro-AET, 5-MeO-MET, and 7-F-5-MeO-MET, among others.

History #

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=10)]

Bretisilocin was first described in the literature in 2021.[[9]](#cite_note-HughesKleinAustin2022-9) [10] It was

[patented](/wiki/Patent)by Andrew Kruegel at

[Gilgamesh Pharmaceuticals](/wiki/Gilgamesh_Pharmaceuticals).

The drug was encountered as a novel

[[10]](#cite_note-WO2022256554-10)[recreational](/wiki/Recreational_drug)

[designer drug](/wiki/Designer_drug)in March 2026.

[[5]](#cite_note-Aipsin-5)## Society and culture

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=11)]

Names

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=12)]

*Bretisilocin* is the [generic name](/wiki/Generic_term) of the drug and its [INN](/wiki/International_Nonproprietary_Name) . [16] It is also known by its developmental code name

GM-2505.

[[1]](#cite_note-AdisInsight-1)

[[9]](#cite_note-HughesKleinAustin2022-9)

[[3]](#cite_note-HughesChristianDvorak2023-3)### Legal status

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=13)]

Canada

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=14)]

Bretisilocin is not a [controlled substance](/wiki/Controlled_substance) in [Canada](/wiki/Canada) as of 2025.[[17]](#cite_note-CDSA-17)

United States

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=15)]

Bretislocin is not an explicitly [controlled substance](/wiki/Controlled_substance) in the [United States](/wiki/United_States). [18] However, it could be considered a

[controlled substance](/wiki/Controlled_substance)under the

Federal Analogue Actif intended for human consumption.

Research #

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=16)]

Bretisilocin is under development as a potential [pharmaceutical drug](/wiki/Pharmaceutical_drug) by [Gilgamesh Pharmaceuticals](/wiki/Gilgamesh_Pharmaceuticals). [1] As of June 2025, it is in

[phase 2](/wiki/Phases_of_clinical_research#Phase_II)

[clinical trials](/wiki/Clinical_trial)for the treatment of

[major depressive disorder](/wiki/Major_depressive_disorder).

A

[[1]](#cite_note-AdisInsight-1)[phase 2a](/wiki/Phases_of_clinical_research#Phase_II)trial of bretisilocin for major depressive disorder has been completed and the

[efficacy](/wiki/Efficacy)and

[safety](/wiki/Drug_safety)data for the trial have been released.

[[1]](#cite_note-AdisInsight-1)

[[19]](#cite_note-PsychedelicAlpha2025-19)

[[20]](#cite_note-Taylor2025-20)The drug has since been acquired from Gilgamesh Pharmaceuticals by

[[21]](#cite_note-Dunne2025-21)[AbbVie](/wiki/AbbVie)in a deal worth up to $1.2 billion.

[[13]](#cite_note-Taylor2025b-13)In 2026 bretisilocin entered

[[14]](#cite_note-PsychedelicAlpha2025b-14)[European Medicines Agency](/wiki/European_Medicines_Agency)’s priority medicines (PRIME) scheme for major depressive disorder.

[[22]](#cite_note-22)

[[23]](#cite_note-23)## See also

[[edit](/w/index.php?title=Bretisilocin&action=edit§ion=17)]

Substituted tryptamineList of investigational hallucinogens and entactogensList of investigational antidepressantsLuvesilocin(RE104; FT-104; 4-GO-DiPT)

References #

[edit]

{{ : CS1 maint: deprecated archival service (cite web}}link) Witkin JM, Golani LK, Smith JL (April 2023).^"Clinical pharmacological innovation in the treatment of depression".Expert Review of Clinical Pharmacology.16(4): 349–362.doi:10.1080/17512433.2023.2198703.PMID37000975.GM-2505 is a dual-acting compound with both agonist activity at 5-HT 2A receptors and a releaser of 5-HT. [...]

[edit]

source & further reading
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